Rear End Conversion

[Russ Brown]

I am 17 years old and would like to change my 1987 1/2ton Chevrolet Silverado rear end to a 3/4 ton rear end for better towing capability. I also own a 22' Pace trailer trailer with (2) 5.000 lb. axles. My trailer and load is approximately 7,800 lbs. I have a small sound and lighting business and can't afford to buy a new truck, but my present truck just dosen't have the power to tow my trailer. I do tow with it but have to be very easy on it. I would like to change rear end to a 3. 73 ratio floating axle for better towing capability. What should I do. I can do the work myself but would like suggestions on the best way to go. I am also thing about changing the transmission to a beefed up 700R4Thanks Russ Brown

[dannyukonxl]

id try to find a rear end and tranny maybe with a drive shaft if your lucky off a junker, you could probably make one off a dodge or ford work also

[dannyukonxl]

welcome to gm-trucks also

[Russ Brown]

What type or model Chevrolet Rear end should I be looking for and how much of a problem will I have with this conversion. Chevrolet rear end 19?? to 19?? and what model truck or vans?

[PFarkas]

I'm sure you'll hear this from other people as well, but I'll say it anyway: It's more expensive to not be able to stop than it is to not be able to go.

 

Swapping a 1500 rear with a 2500+'s rear would probably be easiest if you could get a complete axle assembly from a bone yard, as this will include brakes.

 

Here's one for sale on Ebay for under $200. It's not exactly what you're looking for, but probably similar in price to what you could find locally.

 

A 3/4 ton rear also means a different bolt pattern, which probably means different rims.

 

 

Maybe you could better accomplish your goal by just changing your gears.

[rascal]

if you don't need full floater str, I had a 2500, with semi floater 14 bolt that was 6 lug. mind you i think it's just a bit more HD than the 1/2 ton axle.

[dannyukonxl]

i have no idea about parts matching on those years but with a mig, tig and plasma cutter and a lot of time you can make anything match up, i think the best place to start would be looking for a junkyard 87 3/4 ton pick up and go from there, if not ebay is always helpful

[bigdogs]

I did that on an 80 Blazer I had. I put a 14 bolt full floater in the rear and a Dana 60 in the front. I had to change the U bolts due to different diameters tubs, redo the driveshaft since it had 1310 joints and the 14 bolt had 1350 joints, and obviously change the wheels.

[2500HD4X]

Russ Brown-

Any 73-87 Chevy/GMC 3/4 ton rearend should work on this swap. I would recommend trying to get a complete axle assembly out of a 3/4 ton truck w/all of the braking components. There will be some minor modifications-but the spring perches/shock mounts should be the same. The only thing you will have to modify will be your driveshaft as the yoke sizes are bigger on the 3/4 rearend and you will have to get a set of 8 lug rims for the back- You didn't mention in your post if the truck is 4 wheel drive- If it is you need to be sure and match the front and rear gears.

I wouldn't recommend towing a lot with a 700r4....I have been through several. It is not really suitable for towing in stock form and it is expensive to beef it up. A turbo 400 is where its at for towing on these year models-, but if you do tow w/your 700r4-get a big tranny cooler and do not tow in overdrive. Heat kills a 700r4 quick! Good luck w/your truck!

[awdvkd]

I've done what you are wanting to do twice. Just get an old 14 bolt full floater out of a 73-87 3/4 ton truck. They are cheap and easy to find. It will slide right in, the perchs match and the brakes need very little modifications. Try to find a 4.10 ratio, as for the 700r4 they can be used for trailering as long as you don't try to pull to hard, just let the tranny do the work at its pace not yours. Also remember to always tow in drive not overdrive, add the biggest tranny cooler you can find. Also putting synthetic in the tranny will give you a little insurance. As for the u joints they make a combination joint that will work. All you need to do is find out what each end was and get the right combination. I repeat you do not need to modify the drive shaft. If you find a 14 bolt and the brakes are bad don't replace the drum brakes, convert them to disc. This will can be done for less than replacing the drums. Also the disc brakes will double your braking abilities. Of course you are going to have to get two eight bolt rims for the rear axle. If you want to keep the 15 in rims you can grind the calipers and then the 15in rims will fit. Its really easy go for it. Of course this is if you have a 2 wheel drive truck. If not buy a old junker of a truck and use both axles out of it, they all just slide in 2 wheel or four wheel drive.

[PFarkas]

So far AWDVKD has about the most complete punch list I've seen

 

To summarize:

• Get a 14bolt FF w/ 4.10 gears from a 73-87 3/4ton. How are these identified (gear ratio) when they are off the truck in the boneyard? How can you tell if it's got a locker?
  
• Get the biggest tranny cooler you can find.
  
• Replace U-Joint on driveshaft - they are available to interface a 1/2 ton driveshaft to a 14bolt diff.
  
• If the brakes on the 14bolt are bad, convert them to disc. Converting to disc increases stopping ability.
  
• Get new rims to match the bolt pattern on the replacement axle - 15 inch rims will not fit without modifying the brakes, which are assumed to be converted to disc, and don't think about putting 15" rims on 3/4ton drum brakes.
  
• Get the speedometer corrected
  

 

Would this really be better than re-gearing the diff he's already got and adding a trans cooler? Certainly keeping the 10bolt rear isn't as cool as replacing it with a bigger one, but it looks like it would be a lot cheaper. As long as the original poster isn't replacing the front brakes on the truck, the transmission, or the leaf packs in the rear, even with the 14bolt rear he'll still have other weak areas. Of course, if you're seriously considering upgrading all of those systems, a replacement truck is pretty reasonable.

 

 

Maybe someone can give the original poster a solid idea about what everything will cost, specificly wrt the trans cooler.

[Cool Zr2]

Why don't you just put 3.73's in the 8.5 rear? It can handle it. Not to be negative but that truck isn't going to make enough torque to tear the 8.5 up anyway. Heck, my neighbor has a 95 6.5 Turbo and it is a 1/2 ton with a 8.5 rear, and he haules cats and heavy equipment for his job and its got like 150k on it and everything is perfect.

 

I'd run that 8.5 untill it blows, I'd put money on that it goes forever.

[bigdogs]

If you are really worrying about beefing up the drivetrain to tow, why would you want to use that "cross" u-joint instead of getting the proper 1350 one? If the thing breaks in the middle of nowhere do you want to hope and pray you can find one of those special ones?? Not me that is why I had a new 1350 yoke put on the driveshaft. (which eventually got replaced when the lift kit was installed)

 

The locker that is on those are the gov locks (which don't work as well as these newer G80s) I tossed that and replaced it with a detroit locker.

[awdvkd]

One of those "cross" u-joints are as familiar as any u-joint in a parts store. THis is due to that this change over has been done so many times that you can walk into most parts houses and they know them off the top of their heads. Anybody that has used a truck like a truck knows all you have to do is just jar that 8.5 in diff just once with a heavy load and you will explode the spider gears. I have seen people do it all the time on dirt not to mention asphalt. That doesn't even start to mention the baby brakes that are on an 8.5 in diff. As far as cost I have never had to buy a 14 bolt. They are everywhere and most poeple give them to you if you look long enough. I find them in fields, trucks that have parted out, ect. I believe I had about three hundred dollars in the truck the last time I did it and that included the disc changeover and all new seals. There reason this change over is so popular is that it takes care of everything other than adding a leaf or two and its basically ready to tow. Heck most of the time the two rims needed are already on the rear end. Just run 16 in rims on the back. I may be a back woods hillbilly but once you change the diff, add a leaf spring or two and upgrade the brakes you have a 3/4 ton truck, as close as I care to get for 300.00 bucks. I think its money well spent. Believe me you can't hurt a 14 bolt diff.

[Russ Brown]

Hi, I am Russ Brown who originally posted the conversion for my 1987Chevrolet 1/2 ton two wheel drive truck. I have considered getting rid of the truck for a newer model but just haven't been able to find one that was in as good of shape for less that $10,000. My truck looks like new and I figure that with a few modifications as my labor is free and there are a lot of cheap parts for a Chevrolet truck, I just as well keep the truck and modify it to suite my needs. It seems that I have several options.

1. Keep the present rear end and upgrade to a 4.10 ratio with a larger rear end cover to hold more grease. Cost of gears approximately $150.

2. Look for a 3/4 ton complete rear end and change the drive shaft. Cost of rear end $200. drive shaft modification? New tires $200. Rims $25.00 each. Change brakes to disc cost?

3. What would I need to do to change the front wheels over to match rear wheels. What parts would I need and how difficult is it to change front spindles etc.

4. The transmission in my truck is just about gone so I can buy another one from GM for approximately $1,200. 3 year warranty add a cooler, install myself.

5. Would you suggest buying a beefed up tyransmission from a truck specialist.

6. I do have a Turbo 400 transmission that I could modify, but like the 700R$ with it's overdrive for everyday driving.

6. My trailer has 5,000 lb. axles with good brtakes, it will easily hold back the truck when you apply the electric brakes. My trailer gross load is approximately 7,800lbs. I also use a equalizer hitch with sway bars. I have towed the trailer for about 6 months, it is ok if you drive slowly and don't get into any lugging situations. I do realize that I need a 3/4 ton minimum truck, but a ton would actually do the job much better. I am looking to spend around $3,000 in parts (cheap labor) I can't afford to spend $10,000.

8. Someone told me the frame wasn't strong enought for towing this kind of load. I can easily add beefed up gussets and box the rear end.

 

Thanks for your many responses and I do greatly appreciate all suggestions as I am sure many people have been in the same situation of not having enought money to do what you want.

 

Russ Brown